From the standpoint of host mortality the two most important pathologic alterations in trichinellosis are myositis and myocarditis. The reproductive success of adult Trichinella spiralis will have a substantial influence on these lesions. A recent study by the P.I. suggests that the crowding effect operative against fecundity in adult T. spiralis is a function of competition between adult worms for host dietary carbohydrate. A detailed study on the effects of the quality and quantity of host dietary carbohydrate (glucose, cornstarch, fructose, sucrose, mannose, maltose, trehalose and galactose) and amino acids on the size, number, distribution, fecundity and sex ratio of adult T. spiralis; on the infectivity of newborn larvae; on the numbers of larvae becoming established in the muscles of the host; on the development of host enteritis; and, on acquired resistance inthe host to infection will be conducted. These studies will fill a large gap in our knowledge of the relationship between host diet and the course of trichinellosis. In so doing they will promote our understanding of the quality and quantity of host dietary components that best support the reproductive succes of T. spiralis and thereby have the greatest influence on pathogenesis in trichinellosis.